Simple pretrained model loading

[danieldk]

It would be nice if there was support for loading pretraining models from https://blob.danieldk.eu/sticker-models/ . Just something like

tagger = sticker.pretrained_tagger("de-pos-ud")

E.g. spaCy has such functionality. But their models are actually Python packages. We can't really do that, because the models are also for vanilla sticker.

I have to think a bit about how to handle this. E.g. it would be nice if the models could also be installed with a package manager and it would also be picked up by the Python module.